Serial Management Controllers (SMCs)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
29-12
Freescale Semiconductor
29.3.5
Data Handling Modes: Character- and Message-Oriented
UART mode uses the same data structures as other modes. The structures support multi-buffer operation
and allow break and preamble sequences to be sent. Overrun, parity, and framing errors are reported via
the BDs. At its simplest, the SMC UART controller functions in a character-oriented environment,
whereas each character is sent with the selected stop bits and parity. They are received into separate 1-byte
buffers. A maskable interrupt can be generated when each buffer is received.
Many applications can take advantage of the message-oriented capabilities that the SMC UART supports
through linked buffers for sending or receiving. Data is handled in a message-oriented environment, so
entire messages can be handled instead of individual characters. A message can span several linked
buffers; each one can be sent and received as a linked list of buffers without core intervention, which
simplifies programming and saves processor overhead. In a message-oriented environment, an idle
sequence is used as the message delimiter. The transmitter can generate an idle sequence before starting a
new message and the receiver can close a buffer when an idle sequence is found.
29.3.6
SMC UART Commands
Table 29-5
describes transmit commands issued to CPCR.
Table 29-6
describes receive commands issued to CPCR.
Table 29-5. Transmit Commands
Command
Description
STOP
TRANSMIT
Disables transmission of characters on the transmit channel. If the SMC UART controller receives
this command while sending a message, it stops sending. The SMC UART controller finishes
sending any data that has already been sent to its FIFO and shift register and then stops sending
data. The TBPTR is not advanced when this command is issued. The SMC UART controller sends
a programmable number of break sequences and then sends idles. The number of break
sequences, which can be zero, should be written to the BRKCR before this command is issued to
the SMC UART controller.
RESTART
TRANSMIT
Enables characters to be sent on the transmit channel. The SMC UART controller expects it after
disabling the channel in its SMCMR and after issuing the
STOP
TRANSMIT
command. The SMC UART
controller resumes transmission from the current TBPTR in the channel’s TxBD table.
INIT
TX
PARAMETERS
Initializes transmit parameters in this serial channel’s parameter RAM to their reset state and should
only be issued when the transmitter is disabled. The
INIT
TX
AND
RX
PARAMETERS
command can also
be used to reset the transmit and receive parameters.
Table 29-6. Receive Commands
Command Description
ENTER
HUNT
MODE
Use the
CLOSE
RXBD
command instead of
ENTER
HUNT
MODE
for an SMC UART channel.
CLOSE
RXBD
Forces the SMC to close the current RxBD if it is currently being used and to use the next BD in the
list for any subsequently received data. If the SMC is not receiving data, no action is taken.
INIT
RX
PARAMETERS
Initializes receive parameters in this serial channel parameter RAM to reset state. Issue it only if the
receiver is disabled.
INIT
TX
AND
RX
PARAMETERS
resets both receive and transmit parameters.
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